In the context of biofilm formation, planktonic bacteria are best described as bacteria that _____.

• A. are obligate intracellular pathogens that replicate only inside host cells
• B. exist only as dormant endospores until nutrients become available
• C. live as free-floating, individual cells suspended in a liquid environment
• D. are permanently attached to a surface and embedded in an extracellular polymeric substance (EPS) matrix

Answer: (C)

Verified step by step guidance

1. Understand the term 'planktonic bacteria' in microbiology: these are bacteria that exist as free-floating, individual cells in a liquid environment rather than being attached to a surface.
2. Recognize that biofilms are structured communities of bacteria that are attached to surfaces and embedded in a self-produced extracellular polymeric substance (EPS) matrix.
3. Differentiate planktonic bacteria from biofilm-associated bacteria by noting that planktonic bacteria are not attached to surfaces and are motile or suspended in liquid, whereas biofilm bacteria are sessile and embedded in EPS.
4. Eliminate incorrect options by matching definitions: obligate intracellular pathogens replicate inside host cells, dormant endospores are inactive forms, and bacteria permanently attached to surfaces are biofilm bacteria, not planktonic.
5. Conclude that the best description of planktonic bacteria is that they live as free-floating, individual cells suspended in a liquid environment.